68 Replies - 4651 Views - Last Post: 14 November 2012 - 11:30 PM

Re: Ambidexterity

Posted 13 November 2012 - 10:24 AM

There's a lovely bit of speculation from William Calvin on the origins of right-handed dominance in the human gene pool. It's outlined in the introductionto his collection The Throwing Madonna, although you have to buy the book to get the full exposition.

In a nutshell, it looks like this:

Human heartbeat serves to pacify infants. (experimental evidence on modern infants confirms this)
Human heartbeat is louder on the left side of the chest.
Therefore human child carried in left arm is quieter than same child carried in right arm.
Therefore, mother who can carry child in left arm and throw accurately and forcefully with right arm is more likely to have her offspring survive to reproduce.
Therefore, right-hand dominance has a mild evolutionary advantage in a primitive population, and can be expected to establish itself in the absence of any forces to the contrary.

Re: Ambidexterity

Posted 13 November 2012 - 10:30 AM

h4nnib4l, on 13 November 2012 - 05:12 PM, said:

@strawhat - how does that help me be born a lefty, forced to use my right hand by closed-minded religious people, and then end up ambidextrous? I feel robbed about the ending-up-ambidextrous thing, not the extra crispy thing.

I was offering you the other superstition about being born a lefty. Though, being roasted may help you be born a lefty if the rebirth crap is true.

Handedness strongly aligns to brainedness. ( Is brainedness a word? Screw it, I like it. ) The right hemisphere of the brain generally controls the left side of the body and vice versa. So, the Artist ( right brain ) tends to left handed, the Prince ( I'm thinking Machiavelli here ) tends to be right handed. Simply, the evolutionary advantage of left brained individuals in human society would seem to outweigh those of right brained.

ishkabible, on 13 November 2012 - 12:17 PM, said:

Frequently people were accused for being witches/warlocks as a means of getting someone out of the way.

Wait, when did that stop? If it's no longer witch, warlock, heathen, pinko, commie, homosexual, terrorist, then which is the label to use to instantly demonized your enemies?

Re: Ambidexterity

Posted 13 November 2012 - 11:30 AM

baavgai, on 13 November 2012 - 01:15 PM, said:

Fascinating. I think the answer is simpler than that.

Handedness strongly aligns to brainedness. ( Is brainedness a word? Screw it, I like it. ) The right hemisphere of the brain generally controls the left side of the body and vice versa. So, the Artist ( right brain ) tends to left handed, the Prince ( I'm thinking Machiavelli here ) tends to be right handed. Simply, the evolutionary advantage of left brained individuals in human society would seem to outweigh those of right brained.

There's a chicken/egg question here, I suppose. Where does "brainedness" (good word) come from? Does it possibly derive from handedness?
As for Calvin's story, it's a fun one, but that about all it has going for it, unless/until some convincing support for it turns up. Mostly, I like it as an example of the sort of story telling you can do in evolutionary biology.

Re: Ambidexterity

Posted 13 November 2012 - 12:18 PM

Liked the video.

jon.kiparsky, on 13 November 2012 - 01:30 PM, said:

Does it possibly derive from handedness?

It's a reasonable hypothesis, but I doubt it. The brain is pretty consistent in it's dominance and how it processes. Also, for handedness to play a role, you'd need to get to the point were hand were actively participating an infant's discovery of the world. However, a baby will reach out with a dominant hand before it can even see. I'm going with brain first, hand later.

Strangely, eye dominance is far more fluid. "Cross-dominance", right hand/left eye or left hand/right eye offers some advantage in certain physical activities. I'm right handed but left eye dominant. I suck an sports. However, I suppose it helps in archery.

@NeoTifa: People generally draw the bow with their dominant hand. So, um, no.